A Hawaiian stairway to heaven—that you can't climb.

A toxic ghost town sitting atop a massive coal fire.

Picturesque ruins once held off mighty armies.

Museum about life, death, and cannibalism in the Stone Age.

The stately remains of Llywelyn the Great's mighty fortress.

Northern Ireland's Brobdingnagian stepping stones.

Dublin's "Dead Zoo" serves as a window to Victorian museum design.

The gorgeous library at Trinity College is home to remarkable treasures of Irish identity.

An Irish church where an 800-year-old mummy is reaching out of his coffin as if to shake hands.

Virgil's many-mouthed gateway to the underworld.

Pompeii's less famous neighbor is still revealing her secrets.

This attraction was abandoned after the Chernobyl disaster.

The ghost town left by the worst nuclear disaster of all time is being taken over by nature and urban explorers.

Robots, lasers, and whoopee cushions, oh my!

Shop of curiosities with a dinosaur museum tucked in its basement.

World's second largest particle accelerator, where nature reveals its secrets.

Home to the world's largest refracting telescope and the birthplace of modern astrophysics.

A bizarre house filled with an astounding array of collections.

A fifth-century temple improbably built into the side of a cliff.

A small town Romanian cemetery filled with darkly humorous gravestones.

Home of the world's largest crocodile.

A natural gas leak provides a flickering flame beneath a waterfall.

This hospital once pioneered the use of electroencephalograms, but fell into maltreatment, abuse, and eventual abandonment.

Forgotten German bunkers in China create a sharp cultural contrast.